Safety pressure-relieving device



March 30 {1926. 1,579,141

R. c. PIERCE SAFETY PRESSURE RELIEVING 1JEVICE Filed Sept. 25, 1922 Patented Mar. 30, 1926.

UNITED STATES 1,579,141 PATENT OFFICE.

RAYMOND C, PIERCE, OF NEW YORK, N- Y., ASSIGNOR TO THE LINDE AIR PRODUCTS COMPANY, A CORPORATION OF OHIO.

SAFETY PRESSURE-RELIEVING DEVICE.

Application filed September 1922. Serial No. 590,552.

To all wlzmn it may concern:

Be it known that I, RArMoNn (l. lncnon, ,1. citizen of the United States, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Safety Pressure-Relieving Devices, of which the following is a specification.

This invention relates to safety pressure relieving devices used to protect pressure storage cylinders, refrigeration circuits of refrigerating plants, and other types of pressure storage vessels in which an excesssive or dangerous pressure may develop.

Various types of pressure relieving devices have already been used. One type comprises a copper disc backed by soft fusible metal, the latter melting upon being overheated and so weakening the copper disc that it is burst by excessive pressure. Another type consists solely of fusible metal which will not operate by pressure alone but allows the gas to escape when the cylinder becomes overheated and the fusible metal weakens or melts. In another type a plain copper disc is employed which may fall from a combination of bending and tension or bending and shear depending on whether the disc clamping means has a rounded or square corner.

In those devices employing fusible metal the latter does not always melt in time to save the receptacle from over-pressure. For example, a cylinder of compressed gas placed on a very hot floor may explode from over-pressure before the fusible metal melts. Devices employing, copper discs alone are very unreliable. If the pressurem the storage receptacle rises almost to the disc failure point, a later application of pressure will generally cause the disc to fail at a much lower pressure than intended, in fact these discs seldom fail at the pressure desired. The bursting pressure in such devices is also considerably affected by the machining of the clamping parts.

The object of this invention is to provide a safety pressure relieving device that 1s more dependable than those now generally in use. According to this invention, greater accuracy and certainty may be obtained by jeliminating all stresses except the shearing stresses and using a copper or other suitable metal disc of fairly hard material so that the elastic limit and ultimate strength thereof will be close together. A desirable embodiment of the invention comprises :1 casing carrying a pressure relieving member that closes the pressure receiving chamber of said casing and has a relatively thin annular edge portion clamped to said casing. Centrally said member carries one or two relatively thick masses of slightly less area than the said ehan'lbcr which prevent the bending of the pressure relieving member. The periphery of the mass on the pressure side of said member forms an abrupt shoulder with the thinner marginal portion so as to cooperate with the closely adjacent clamping means and casing to shear such thinner marginal portion and release the predetermined excessive pressure when it occurs.

The objects and novel features of the invention will be apparent from the following description taken in connection with the drawings in which- Figs. 1 and 2 are respectively a top plan view and a vertical sectional view of a safety pressure relieving device embodying this invention; and

Figs. 3 and 4; are a sectional view and plan view, respectively, of another type of pressure relieving element embodying this invention.

Referring to Figs. 1 and 2, the pressure relieving device may consist of a relatively thin frangible substantially circular disc 1) of relatively hard copper or other suitable metal and a much thicker central reinforcing or loading body of smaller diameter comprising masses of metal such as separately formed washers C and E secured to opposite faces of the disc by a central rivet R, or by soldering, welding or other means. One of these washers or central reinforcing masses may be omitted if desired. Since the washers are of smaller diameter than the disc, a relatively narrow thin marginal portion P is provided whereby the pressure relieving device may be secured to a suitable holder adapted to be mounted on a pressure storage vessel to be protected.

Figs. 3 and 4: illustrate another type of pressure relieving element embodying this invention in which the central thicker mass M has a much thinner annular marginal portion P formed integral therewith, as by turning down annular edge portions of a disc of the thickness of the central part M. In this type also, the thicker mass may be disposed on one orboth sides of the plane of the thin marginal portion: 1, and may consist of relatively hard copper on other suitable metal.

The improved pressure relieving clement mav be secured in a suitable holder adapted to communicate;with the pressure storage vessel to be protected? As illustrated in Figs. 1 and 2, the holder may comprise a casing in the form of a plug having a threaded stem T that: is adapted to tit. into a threaded hole in a gas storage cylinder, for example. This plug has a central passage T that may communicate with the intei'ior of the cylinder and opens into a chainher H located in the enlarged head A which maybe of hexagon or other shapeto take a wrench. A suitable annular shoulder S in the chamber provides a seat for the annular marginal portion P or 1 of the pressure relieving device. A cap B or other suitable means may be employed to clamp the marginal portion or P against the seat S teproduce a gasrtight 1o1nt. The cap ll is desirably threaded to titcorrespondinglthreads in the head A, is hollow to provide a tlltlnl ber B and has a series of apertures B to allow the escape of gas or liquid from said chamber.

The peripheries of the washers C and E and metal masses M desirably providesharp or abrupt shoulders L and L on the pressure relieving device of slightly less diameter than the opposed walls of the chambers H and B, the latter presenting sharp or right angle corners to the thin marginal part P clamped therebetween. The marginal portions P and P are decidedly thinner than the central metal masses; as shown, these central masses are at least four times as thick as the marginal portions of the discs. The shearable section is a part of the thin marginal portion and is in the same plane as the latter and just outside the periphery ofthe central reinforcing mass. The central metal masses prevent bending in the pressure relieving device and failure of the latter can only occur because of shearing stresses in that portion bf the thin marginal part P that bridges the gap between the walls of the chambers H and B and the peripheries of the central reinforcing masses.

The device operates in the following manner: Pressure is applied through the passage T into the chamber H and over the area of the washer C. but because of the reinforcement provided by the latter, there will be no bending nor tension in the pressure relieving device. The stress is then resisted by the shearing strength of the marginal portion. the shear surfaces being the corner of the washer C that abuts against the pressure side of the disc D, and the lower inner corner of the cap that is clamped against the upper side of the marginal portion I. \Vhen the pressure within the rehamber IT exceeds the shearing strength 'of this marginal portion of the disc, the latter will bef'eut and the central part of the disc D together with the washers C and lhr'will be blown into the upper part; ot the chamber ll, the high pressure gas or liquid beingrelieved by passing around the washers and disc and outthrough the passages li into the atmosphere. The element shown in Figs. 3 and 4 may bev substituted to! the Yme shown in Figs. 1 and 2 and operates in a sinrilar manner.

Variouschanges may be made in the details of construction shown without saeri tiring the. advantages of the invent-iomand aecordingl the invent'ionis not intended to be limited to the exact arrangcmentdisclosed. I

I claim l. A safety pressure relieving device having a't'hin annular marginal portion adapted to be secured to a suitable holder, and" a much thicker reinforcing mass united to and disposed centrally within said annular portion, said annular portion comprising a narrow section adapted to be sheared at a predetermined pressure by the cooperation of the periphery of said reinforcing mass with a part off said holder.

2. A safety pressure relieving device com prising a sheet metal disc having an' annular marginal portion adapted to be secured] to a suitable holder, and a reinforcing mass 1100 of metal secured to the central portion of said sheet metal disc, said annular marginal portion comprising a narrow section adapted to be sheared at a predetermined pressure by the cooperation of the periphery of said reinforcing mass with a part of said holder. 7r

3. A. safety pressure relieving device comprising a relatively thin metal disc and a separately formed thicker metal mass' of smaller diameter secured to the high pressure side thereof, leaving a free marginal portion of said disc whereby the device may be secured to a suitable holder, such metal mass preventing the bending of the central part of said disc and having a peripheral edge cooperating with said holder to shear said disc to relieve excessive pressure.

4. A safety pressure relieving device comprising a relatively thin disc and washers of smaller diameter secured to opposite faces thereof, leaving a free marginal portion of said disc whereby said device may be secured to a suitable holder. such washers preventing the bending of the central part of said disc but allowing said device to fail outside the boundary of said washers.

5. A safety pressure relieving device comprising a sheet metal disc, reinforcing means of smaller diameter than said disc, and

being disposed close to and adapted to corivet means securing said reinforcing means centrally to disc.

6. A safety pressure relieving device according to claim 5, in which said reinforcing means comprises washers secured against opposite faces of said disc.

7 The combination with a holder having a chamber adapted to communicate with a pressure vessel, of a safety pressure relieving device having a thin annular marginal portion secured to said holder, and projecting slightly within said chamber to provide a narrow annular shearable section adjacent the inner wall of said chamber, and a mass of metal carried centrally by' and considerably thicker thansaid marginal portion and spaced from the inner wall of said chamber by the width of said shearable section, the periphery of such metal mass frangible substantially circular disc having an annular marginal portion secured to said holder, and a relatively heavy mass of metal secured to the central portion of said disc within said chamber, the periphery of said mass of metal being constructed and arranged to cooperate with the inner wall of said chamber to shear the adjacent por-' tion of said disc at a predetermined pressure.

In testimony whereof, I afiix my signature,

RAYMOND C. PIERCE. 

